How to make curves with empty intervals in them?

[Astronomy]

Yes the first is just a horizontal line.

The Array of constant functions will produce this:

"_________ _________ ______________"
f1(1). .......f2(1) .........f3(1)

three or more f(..) at the same y-position, but with different x-points will possibly work..

greetz AP.

[Uwe]

1) If you want to display a curve with gaps overload QwtPlotCurve::drawXY ( don't use markers ).
2) By curve->setItemAttribute(QwtPlotItem::Legend, ...) you can control if a curve ( or any other QwtPlotItem ) should have an entry on the legend.

Uwe

[alex_sh]

Thank you both.
I solved this by creating multiple curves and disabling the legend items (using setItemAttribute()) on all of them except the first one.
Note that I had to disable the legend item _before_ the attach() call, or it would still allocate the space in the legend, but draw nothing there.

P.S. There's no QwtPlotCurve::drawXY() in Qwt6, or am I mistaken?

[Galak]

Hi,
I have resolved this problem to using nan values, see the attached files
qwt_plot_piecewise_curve.h
qwt_plot_piecewise_curve.cpp